1. Field of the Invention
The present invention relates generally to knock sensor systems and, more specifically, to a knock sensor diagnostic system for an internal combustion engine.
2. Description of the Related Art
Generally, normal combustion in a spark ignition internal combustion engine occurs when part of a fuel mixture is ignited by a spark from an ignition plug and a resulting flame spreads out into the fuel mixture. Knocking occurs in this process when part or all of the uncombusted fuel mixture ignites itself before propagation of the flame. This self ignition is caused by an increase in temperature due to the compression of the fuel mixture. The knocking of the engine causes a rapid increase in pressure in the combustion chamber and the propagation of a pressure wave which result in mechanical vibration in the engine components and overheats the ignition plugs and engine components.
Various kinds of knock sensor systems have been designed to detect vibration sounds, mechanical vibration acceleration, or combustion internal pressure vibrations of an internal combustion engine. The detection of this engine knock is desirable in that engine operating parameters can be adjusted to avoid such a condition.
Now, under federal regulations, the various knock sensor systems must also include a knock sensor diagnostic system. The diagnostic system will be used to test the integrity of the knock sensor system and report any detected problems to the operator.